Journeyman Electrician Exam (NEC) flashcards

When a building's metal frame is used as a grounding electrode, the grounding electrode conductor (GEC) is sized according to NEC Table 250.66, based on the size of the service-entrance conductors.

• Building steel is a common type of grounding electrode.
• GEC size determined by NEC Table 250.66.
• Based on the largest ungrounded service-entrance conductor size.

Memory trick: Steel Frame GEC: Service size dictates the gain!

National Electrical Manufacturers Association (NEMA) standards define electrical receptacle and plug configurations for various voltage and current ratings.

• Identifies voltage, amperage, and grounding type.
• Ensures compatibility and safety.
• Commonly seen as 'straight blade' or 'locking' types.

Memory trick: NEMA: Number, Amps, Volts, and Ready for Use.

Equipment grounding conductors are required for an ungrounded system to provide a ground-fault current path, even though there is no grounded (neutral) conductor to connect to.

• EGCs are mandatory for equipment in ungrounded systems (NEC 250.4(A)(3)).
• They establish a ground-fault current path to the supply source.
• Connect to the equipment grounding terminal bar in panelboards.

Memory trick: Delta's ground: Equipment still needs a path!

NEC Article 430.72 dictates the minimum size for motor control circuit conductors based on their overcurrent protection and proximity to power circuit conductors to ensure mechanical strength and adequate current-carrying capacity.

• Generally, control circuit conductors must not be smaller than 14 AWG.
• Smaller conductors (16 AWG or 18 AWG) are permitted if the control circuit is protected by an overcurrent device rated 10A or less.
• An exception applies when control conductors are in the same raceway as power conductors, requiring larger sizes if the power circuit protection exceeds 20A.

Memory trick: Control wires are small, but they need big protection if they're with the big guys.

The maximum continuous current rating for motor overload protection is determined by the motor's full-load current (FLA) and its service factor or temperature rise rating, as specified in NEC 430.32.

• Motors with a service factor of 1.15 or greater, or a marked temperature rise not over 40°C, are protected at not more than 125% of FLA.
• All other motors are protected at not more than 115% of FLA.
• Overload protection devices prevent motor damage from sustained overcurrents.

Memory trick: Service Factor dictates the Safety Factor for your motor's protection.

The minimum size for a copper grounding electrode conductor connected to a driven ground rod is No. 6 AWG, regardless of the service size, as per NEC® 250.66(A).

• Applies to rod, pipe, and plate electrodes.
• Minimum size is No. 6 AWG copper.
• Service size does not increase this minimum for these specific electrodes.

Memory trick: Six Gauge for Sticks and Plates, no matter the Amps.

A Ground-Fault Circuit-Interrupter (GFCI) is a fast-acting circuit breaker designed to shut off electric power in the event of a ground-fault within as little as 1/40 of a second.

• Detects current leakage to ground.
• Protects personnel from electric shock.
• Required in many wet or damp locations by the NEC.

Memory trick: GFCI: Ground Fault, Current Interrupted, Safe Individuals.

The protective device (e.g., circuit breaker) that limits the current flowing through a branch circuit to prevent damage to conductors and equipment.

• Rating must not exceed conductor ampacity, with some exceptions.
• Protects against overloads and short circuits.
• Standard ratings are specified in NEC 240.6(A).

Memory trick: Circuit's shield must match its strength.

Overcurrent protection for hermetic refrigerant motor-compressors, specifically sized according to NEC Article 440, considering both rated-load and starting currents.

• NEC 440.22(A) governs sizing.
• Initial maximum is 175% of Rated-Load Current (RLC).
• Can be increased to 225% of RLC if needed for starting.
• RLC is used, not FLA from Article 430 tables.

Memory trick: Hermetic Fuse: RLC x 175%, then 225% if needed.

NEC 430.24 outlines the requirements for sizing feeder conductors supplying a group of motors, ensuring adequate ampacity by considering the largest motor's FLA at 125% and adding the FLAs of all other motors.

• Feeder ampacity = (125% * FLA of largest motor) + (sum of FLAs of all other motors).
• This rule applies to feeders supplying two or more motors or a motor(s) and other loads.
• The 125% factor for the largest motor accounts for its starting current and continuous operation.

Memory trick: Feeders for groups: Big motor gets a bonus, others just add up.

Metal water piping systems must be bonded to the electrical service to ensure all metallic systems are at the same potential, preventing shock hazards and providing a low-impedance fault path, as per NEC® 250.104(A)(1).

• Required for metal water piping in or attached to a building/structure.
• Bonding point: service equipment, grounded conductor, GEC, or grounding electrode.
• Applies whether or not the piping is used as a grounding electrode.

Memory trick: Water pipes must be tied to the service, like a lifeline for safety.

NEC 430.22(A) requires that motor branch-circuit conductors for continuous duty motors have an ampacity not less than 125% of the motor's full-load current (FLA) to ensure they can safely carry the motor's running current and accommodate minor overloads.

• Conductor ampacity is calculated as 125% of the motor's FLA for continuous duty motors.
• This sizing accounts for normal operating conditions and minor, sustained overloads.
• The FLA is typically obtained from the motor nameplate or NEC Tables 430.247 through 430.250.

Memory trick: For Continuous Duty, Conductors need a Quarter More power.

NEC 430.102 mandates specific location requirements for the motor controller disconnecting means to ensure safety during maintenance and repair, primarily requiring it to be within sight of the controller or capable of being locked in the open position.

• The disconnecting means must be within sight from the controller location.
• Alternatively, it can be out of sight if it is capable of being locked in the open position.
• This ensures that personnel working on the controller can safely de-energize it.

Memory trick: See the disconnect, or Lock it, so no one gets shocked.

Motor control circuits are typically categorized as two-wire or three-wire, referring to the number of control conductors connecting the control device to the starter coil, which determines the motor's restart behavior after a power interruption.

• Two-wire control provides automatic restart upon power restoration (undervoltage release).
• Three-wire control provides undervoltage protection, requiring manual restart after power restoration.
• Three-wire control is generally safer as it prevents unexpected motor restarts.

Memory trick: Two wires: Automatic return. Three wires: Manual turn.

The main bonding jumper connects the equipment grounding conductor(s) and the service equipment enclosure to the grounded conductor at the service and is sized according to NEC 250.102(C)(1) based on the service-entrance conductor size.

• Sized from NEC Table 250.102(C)(1).
• Based on the largest ungrounded service-entrance conductor.
• Ensures an effective ground-fault current path.

Memory trick: Bonding Jumper: Service conductor's friend!

The overcurrent protective device (OCPD) on the primary side of a transformer, sized according to NEC Article 450, to protect the transformer from overcurrents.

• NEC 450.3(B) applies for transformers 1000V or less.
• Maximum 125% of primary current if no secondary OCPD.
• Next higher standard rating permitted if calculated value is not standard.

Memory trick: Transformer Guard: Calculate Current, Multiply, Choose Closest.

NEC 430.72(A) outlines the requirements for overcurrent protection of control circuit transformers, including specific exceptions for Class 2 power-limited transformers where protection can be provided by the branch-circuit overcurrent device.

• Primary protection is generally required at not more than 125% of the rated primary current.
• Exception No. 2 allows omission of primary protection for Class 2 power-limited transformers if the branch-circuit OCPD provides adequate protection.
• Secondary protection is also required, typically based on conductor ampacity.

Memory trick: Primary protection: 125% or branch circuit for Class 2, don't let it burn out!

NEC 430.52 specifies the maximum ratings for short-circuit and ground-fault protective devices for motor branch circuits, which vary based on the type of motor and the protective device used (e.g., fuses, circuit breakers).

• These devices protect the conductors and motor from short circuits and ground faults, not overloads.
• Multipliers are applied to the motor's full-load current (FLA) to determine the maximum permitted rating.
• Different multipliers exist for non-time-delay fuses, time-delay fuses, instantaneous trip circuit breakers, and inverse time circuit breakers.

Memory trick: Fuse your motor for faults, not just for fun; multiply FLA by the right one!

A Variable Frequency Drive (VFD) is an electronic device that controls the speed of an AC electric motor by varying the frequency and voltage of its power supply.

• VFDs provide precise speed control and can maintain constant torque.
• They improve energy efficiency by matching motor speed to load requirements.
• VFDs reduce mechanical stress on equipment during starting and stopping.

Memory trick: For flexible motor speed, Frequency is your Friend.

For a metal underground water pipe to be considered an effective grounding electrode, it must have at least 10 ft (3.0 m) of direct contact with the earth, as specified in NEC® 250.52(A)(1).

• Applies specifically to metal underground water pipes.
• Minimum 10 ft (3.0 m) of direct earth contact.
• Must be supplemented by an additional electrode (NEC® 250.53(D)(2)).

Memory trick: Water pipe needs a 'ten-foot dive' to be a good ground.

The calculated load assigned to general-purpose receptacle outlets for the purpose of sizing feeders and services, as specified by the NEC.

• NEC 220.14(I) specifies 180 VA per outlet.
• Applies to general-purpose receptacles, not dedicated circuits.
• Used to avoid oversizing when not all outlets are used simultaneously at full capacity.

Memory trick: Feeder Load: Every Outlet Counts, Even a Little.

The maximum mounting height for the operating handle of a service disconnecting means, as specified by the National Electrical Code, to ensure ready accessibility.

• NEC 230.72(C) sets the limit.
• Maximum 2.0 m (6.56 ft) above working platform.
• Ensures safe and easy operation.

Memory trick: Disconnect Height: Don't Reach, Just Grab.

The main bonding jumper connects the equipment grounding conductor(s) and the service equipment enclosure to the grounded conductor at the service, ensuring an effective ground-fault current path.

• Required at the service equipment.
• Connects non-current-carrying metal parts to the grounded conductor.
• Provides a low-impedance path for ground-fault current.

Memory trick: Bonding: Faults find a path, safely!

The main bonding jumper (MBJ) connects the equipment grounding conductor to the grounded service conductor and service enclosure. Its minimum size is determined by the largest ungrounded service-entrance conductors, using NEC® Table 250.102(C)(1).

• Connects ground and neutral at the service.
• Size derived from the largest ungrounded service-entrance conductors.
• Reference NEC® Table 250.102(C)(1).

Memory trick: MBJ's size mirrors the biggest service wire's might.

Equipment grounding conductors are sized based on the ampere rating of the overcurrent protective device in the circuit, as found in NEC Table 250.122.

• Based on OCPD rating, not conductor ampacity.
• Provides a low-impedance fault path.
• Ensures OCPD operation during a ground fault.

Memory trick: EGC: OCPD's rating determines its size!

Separately derived systems must be grounded to one or more acceptable grounding electrodes as specified in NEC® 250.52(A), which include metal water pipes, building steel, and ground rings, but not isolated conduit.

• Grounding electrodes for SDS must meet 250.52(A) requirements.
• Common electrodes: metal water pipe, building steel, concrete-encased electrode, ground ring, rod/pipe/plate electrodes.
• Isolated metal parts or ungrounded systems are not acceptable electrodes.

Memory trick: SDS needs a solid ground, not just a floating pipe dream.

The equipment grounding conductor (EGC) is sized based on the rating of the overcurrent protective device (OCPD) in the circuit, as per NEC Table 250.122.

• Sized from NEC Table 250.122.
• Based on the ampere rating of the OCPD.
• Not directly on the circuit conductor size, but the OCPD protects the conductors.

Memory trick: EGC: OCPD's protector, Table 122's guide!

The minimum length of conductor required to extend from an outlet box, junction box, or switch box to allow for proper splicing or connection of devices or luminaires.

• NEC 300.14 specifies 150 mm (6 inches).
• Ensures adequate room for making safe and reliable connections.
• Applies to all conductors entering the box.

Memory trick: Box Wires: Six Inches, No Less Than That.

The grounding electrode conductor connected to a metal underground water pipe electrode must be sized according to NEC Table 250.66, based on the size of the service-entrance conductors.

• Applies to metal underground water pipe electrode.
• Sized from NEC Table 250.66.
• Based on the largest ungrounded service-entrance conductor size.

Memory trick: Water pipe GEC: Service conductor's call!

The maximum current that a branch circuit can carry continuously (3 hours or more) without exceeding 80% of the circuit's overcurrent device rating, as required by the NEC.

• NEC 210.23(A)(1) and 210.20(A) specify the 80% rule.
• Applies to most branch circuits with continuous loads.
• Protects against excessive heat buildup in conductors and devices.

Memory trick: Branch Circuit: Continuous Load, Eighty Percent Safe.

For sizing conductors, overcurrent protection, and disconnects for motors, the NEC requires using full-load current values from Article 430 tables, not the motor's nameplate FLA.

• NEC 430.6(A)(1) mandates using table values.
• Tables account for worst-case conditions and design factors.
• Nameplate FLA is for motor overload protection only.

Memory trick: Motor Sizing: Table Trumps Tag for True Current.

Overcurrent protection for motor branch circuits designed to protect the motor circuit components (conductors, control apparatus) from short circuits and ground faults.

• Sized based on NEC Table FLA, not nameplate FLA.
• Multipliers from NEC Table 430.52(C)(1) are used.
• Maximum ratings can be increased if the motor fails to start, up to specific limits.

Memory trick: Motor Fuse: Table FLA, Max Multiplier, Then Standard Size.

The minimum size of an equipment grounding conductor is determined solely by the rating of the overcurrent protective device in the circuit, as specified in NEC® Table 250.122, not by the feeder conductor size.

• Reference NEC® Table 250.122.
• Based on the upstream overcurrent device rating.
• Feeder conductor size is irrelevant for EGC sizing per this table.

Memory trick: The EGC is sized by the breaker's bite, not the wire's might.

NEC 430.52(C)(1) includes exceptions that allow increasing the rating of branch-circuit short-circuit and ground-fault protective devices beyond the standard table values if the motor cannot start, with specific upper limits depending on the device type.

• The standard maximum for inverse time circuit breakers is 250% of FLA (Table 430.52).
• If 250% is insufficient for starting, it can be increased, but not to exceed 400% of FLA.
• Similar exceptions exist for other protective device types (e.g., non-time-delay fuses up to 400%).

Memory trick: If 250% isn't enough, an inverse breaker can go up to 400% for that motor's tough start.

NEC 430.122(A) specifies that conductors supplying the input side of a variable frequency drive (VFD) must have an ampacity not less than 125% of the VFD's rated input current, to account for harmonics and continuous operation.

• The 125% rule applies to the VFD's rated input current, not directly to the motor's FLA.
• This sizing accounts for harmonic currents generated by the VFD.
• The VFD's input current rating is typically found on its nameplate or documentation.

Memory trick: VFD input: A Quarter more power for its fancy dance.

The maximum rating of an inverse time circuit breaker used for branch-circuit short-circuit and ground-fault protection for a squirrel-cage motor is generally 250% of the motor's full-load current (FLA), rounded up to the next standard size if necessary.

• NEC Table 430.52 specifies maximum OCPD ratings.
• For inverse time circuit breakers on squirrel-cage motors, the maximum is 250% of FLA.
• If the calculated value doesn't match a standard OCPD size, the next higher standard size is permitted.

Memory trick: Motor's protection: full current times protection factor, then find the standard fit.

The operating handle of the service disconnecting means must be located not more than 6 feet 7 inches (2.0 meters) above the finished grade or working platform to ensure it is readily accessible.

• NEC 230.70(A)(1) specifies the height.
• Maximum height is 6 ft 7 in (2.0 m).
• Ensures easy access for operation and emergency shutdown.

Memory trick: Easy reach for the main switch, no higher than a tall person's stretch.

For Class 1 motor control circuits, the minimum conductor size and associated overcurrent protection depend on whether the conductors extend beyond the control enclosure. Smaller gauges (e.g., 18 AWG) are permitted for conductors entirely within the control enclosure with appropriate overcurrent protection.

• NEC 430.72(B) and Table 430.72(B) govern control circuit OCPD and conductor sizing.
• Conductors within an enclosure have different rules than those extending outside.
• 18 AWG copper is permitted for 10A OCPD if within the control enclosure.

Memory trick: Control wires need specific protection; inside the box, smaller wires are okay.

The branch-circuit short-circuit and ground-fault protective device for a hermetic refrigerant motor-compressor must be sized between 175% and 225% of the motor-compressor's rated-load current (RLC), with the lower value (175%) being the starting point, rounded to the next standard size.

• NEC 440.22(A) governs this sizing.
• Initial sizing is 175% of RLC.
• Can be increased up to 225% of RLC if needed for starting current.
• Must use standard OCPD sizes (NEC 240.6).

Memory trick: Cool compressor needs its own special protection math: 175 to 225.

For non-dwelling units, the demand load for general-purpose receptacles is calculated using a demand factor of 100% for the first 10 kVA, and 50% for the load exceeding 10 kVA, as per NEC 220.42(B).

• NEC 220.42(B) applies to non-dwelling units.
• First 10 kVA of receptacle load is at 100% demand.
• Load exceeding 10 kVA is at 50% demand.
• This reduces the calculated load for feeder and service sizing.

Memory trick: Commercial plugs: first 10k is full, rest is half.

Dwelling unit garages (attached or detached with power) must have at least one 120-volt, 20-ampere branch circuit dedicated to supplying receptacle outlets within the garage, and it cannot supply other loads.

• NEC 210.11(C)(4) specifies this requirement.
• Minimum of one 20-ampere, 120-volt circuit.
• Circuit must be dedicated to the garage receptacles.
• Applies to attached and detached garages with power.

Memory trick: Garage needs its own strong circuit, just one for all the plugs.

A pilot device is a control circuit component (e.g., push button, limit switch, float switch) that senses a condition or receives an input and then sends a low-power signal to another control device (like a motor starter or relay) to initiate or stop an action, rather than directly controlling the main power circuit.

• Operates in the control circuit, not the power circuit.
• Sends signals to other control devices (e.g., contactors, relays).
• Does not directly switch main motor current.
• Examples include push buttons, limit switches, pressure switches.

Memory trick: Pilot device: a small finger that tells the big hand what to do.

Ground-Fault Circuit Interrupter (GFCI) protection is required for all 125-volt, single-phase, 15- and 20-ampere receptacles located in basements of dwelling units to protect against electrical shock hazards.

• NEC 210.8(A)(5) mandates GFCI for dwelling unit basements.
• Protects against ground faults, which can occur in damp locations.
• Applies to 15A and 20A, 125V receptacles.

Memory trick: GFCI: Wet places get the shock stopper.

For transformers with a primary full-load current of 9 amperes or more, the maximum primary overcurrent protection with fuses is 125% of the primary full-load current. If the calculated value does not correspond to a standard fuse size, the next higher standard size is permitted.

• NEC 450.3(B) governs transformer overcurrent protection.
• For PFLC ≥ 9A, max fuse is 125% of PFLC.
• Next higher standard size is allowed if calculated value is not standard (NEC 240.4(B)).

Memory trick: Transformer's first defense: Current times factor, then standard up.

The NEMA 5-15R is a standard configuration for a 120-volt, 15-ampere, three-prong (grounded) receptacle commonly used for general-purpose applications in residential and commercial settings.

• 5 indicates 125 volts.
• 15 indicates 15 amperes.
• R indicates receptacle.
• It has two vertical slots and a round ground hole.

Memory trick: NEMA codes: Number-Number-Letter tells you Voltage, Amps, and Type.

The Full-Load Current (FLA) for motors, used for sizing conductors and overcurrent protection, is typically obtained from NEC Tables 430.247 through 430.250, rather than the motor nameplate, for consistency and safety.

• NEC Tables 430.247-430.250 provide standardized FLA values.
• These values are used for sizing branch-circuit conductors and overcurrent protection.
• Nameplate FLA is used for motor running overcurrent protection.

Memory trick: For motor sizing, the NEC table knows the true current.

The minimum depth of earth cover required for underground conductors and raceways, as specified in NEC Table 300.5, varies based on wiring method, voltage, and location.

• Protects against physical damage.
• Depths vary for direct burial, RMC, IMC, PVC.
• Special conditions (e.g., under roads, residential driveways) can alter depth.

Memory trick: Dig deep to keep wires safe from harm.

For a one-family dwelling, the service disconnecting means must have a rating of not less than 100 amperes, 3-wire, for a calculated load of 10 kVA or more.

• Applies to one-family dwellings.
• Minimum 100A, 3-wire.
• Triggered by calculated load of 10 kVA (10,000 VA) or more.

Memory trick: Home's main power needs a hundred-amp hero.

The service disconnecting means for each service shall consist of not more than six switches or six circuit breakers, grouped and identified.

• Applies to each service.
• Maximum of six operations to disconnect all power.
• Can be in one or multiple enclosures.

Memory trick: Six Switches Secure the Service.

According to NEC Table 220.54, the demand load for a single household electric clothes dryer is 5000 VA for dryers rated 5 kW or less. For dryers rated over 5 kW, the demand load is 5000 VA plus 100% of the nameplate rating in excess of 5 kW.

• Applies to household electric clothes dryers.
• Minimum demand is 5000 VA.
• Add 100% of excess for dryers over 5 kW.

Memory trick: Dryer Kilowatts: Five for Five, Plus the Excess.

The minimum size of an equipment grounding conductor (EGC) for a branch circuit is determined by the rating of the overcurrent protective device (OCPD) for that circuit, as specified in NEC Table 250.122.

• Size depends on OCPD rating.
• NEC Table 250.122 is the reference.
• Ensures proper fault current path.

Memory trick: Grounding Wire: OCPD Dictates Diameter.

Feeder conductors supplying continuous loads must have an ampacity not less than 125% of the continuous load, plus 100% of any non-continuous loads.

• Continuous load operates for 3 hours or more.
• Conductor ampacity must meet or exceed calculated value.
• Based on NEC 215.2(A)(1).

Memory trick: Feeder Continuous: One and a Quarter, Plus Non-Stop.

Dwelling unit kitchens, pantries, dining rooms, and similar areas must be provided with a minimum of two 20-ampere small-appliance branch circuits to serve receptacle outlets.

• Minimum of two circuits.
• Must be 20-ampere rated.
• Serve receptacle outlets in specific dwelling areas.
• Cannot supply other outlets or equipment, with limited exceptions.

Memory trick: Two 20-amp circuits keep the kitchen flowing.

NEC 110.26(E) specifies the minimum vertical clearance (headroom) above electrical equipment, such as switchboards and panelboards, for safe access and work.

• Minimum 6.5 feet (1.98m) for equipment up to 1000V.
• Applies to service equipment, switchboards, panelboards, motor control centers.
• Ensures sufficient space for personnel and equipment manipulation.

Memory trick: Stand tall, work safely, keep your head clear.

When a grounding electrode conductor (GEC) connects to a ground rod (a made electrode), its minimum size is not required to be larger than No. 6 AWG copper, regardless of the service entrance conductor size.

• Applies to made electrodes like ground rods.
• Maximum required size is No. 6 AWG copper.
• Different rules apply for other electrode types.

Memory trick: Grounding Rod is Six, Concrete is Four, Pipe is Service.

Overcurrent protective devices (OCPDs) for circuits supplying continuous loads must be sized at a minimum of 125% of the continuous load plus 100% of non-continuous loads.

• Continuous load operates for 3 hours or more.
• OCPDs protect conductors and equipment.
• Must use next standard OCPD size if calculated value is not standard.

Memory trick: Continuous Current Calculates Carefully.

Any penetration of a fire-resistant-rated assembly by electrical wiring or equipment must be sealed with an approved firestop system to prevent the spread of fire and smoke.

• NEC 300.21 directly addresses the protection of openings in fire-rated barriers.
• The firestop material must be 'approved' for the specific application and rating.
• Failure to properly firestop can compromise building safety and violate code.

Memory trick: Seal the hole, save a soul!

The smallest gauge of conductor permitted by the NEC for a given overcurrent protective device rating, ensuring safe current carrying capacity.

• Minimum size for 15A circuit is 14 AWG copper.
• Minimum size for 20A circuit is 12 AWG copper.
• Minimum size for 30A circuit is 10 AWG copper.

Memory trick: Small wires for small amps, big wires for big amps, remember the 'AWG current rule'.

Specific wiring methods required in Class I, Division 2 hazardous locations to prevent the ignition of flammable gases or vapors, characterized by the need for sealed or explosionproof integrity.

• Hazardous locations are defined by NEC Article 500.
• Class I, Division 2 means ignitable concentrations are present only under abnormal conditions.
• Wiring methods must prevent gas/vapor entry to prevent ignition.

Memory trick: In Div 2, seal it tight, don't let the gas ignite, EMT is not the 'safe tube'.

The NEC requires a minimum length of free conductor at each box opening to facilitate safe and proper termination and splicing of wires.

• NEC 314.17(C) sets the requirement for free conductor length.
• The minimum length is 6 inches.
• Ensures adequate wire length for future maintenance, device replacement, and proper stripping.

Memory trick: Six inches of slack, for a safe wiring track!